1. Field of the Invention
The present invention relates to an occupant protecting device designed so that an air bag, accommodated within a seat back, is deployed into a vehicle passenger compartment upon collision of a vehicle to protect an occupant.
2. Description of the Related Art
Such a system is known, for example, from Japanese Patent Application Laid-open No. 3-108564. In general, an occupant protecting device of such a type includes an air bag module which has a folded air bag and an inflater.
FIGS. 12A to 12C show a prior art method for folding up an air bag B. As shown in FIG. 12A, the air bag B in a deployed state has a vertical dimension L2 larger than a vertical dimension L1 of the inflater I, and a longitudinal dimension L3 substantially equal to the vertical dimension L2. To fold up the air bag B, upper and lower portions of the air bag B are first folded inwardly, as shown in FIG. 12B, so that the vertical dimension L2 is near to the vertical dimension L1. Then, the air bag B is longitudinally folded into a bellows-like shape, as shown in FIG. 12C, thereby forming a module wherein the inflater I is accommodated within the air bag B.
The air bag B folded up in the above-described manner is deployed in a straight forward direction of a vehicle body from a side of a seat back 2, as shown in FIG. 14. For this reason, there is a possibility that the air bag B cannot be smoothly deployed due to interference with a side and an arm of an occupant. To avoid such a problem, it is necessary to deploy the air bag B obliquely forwardly toward a center pillar 4 and a front door in order to permit the air bag B to properly penetrate into a space between the center pillar 4 as well as the front door 5 and the occupant.
FIGS. 13A to 13C show a course of deployment of the air bag B which has been folded up in the above-described prior art method. The air bag B is first deployed longitudinally as shown in FIG. 13A, and then vertically as shown in FIG. 13B to finally be in a completely deployed state shown in FIG. 13C. If the vertical deployment is performed behind the longitudinal deployment in the above-described manner, there is a problem that the side of the occupant cannot be held back at an initial stage of the deployment over a vertical wide range.
Further, such an occupant protecting device is known from Japanese Patent Application Laid-open No. 8-225054 (hereinafter xe2x80x9cJP ""054xe2x80x9d), in which an air bag is formed by integrally sewing two left and right main basic fabrics with a single side basic fabric to connect outer peripheral edges of the two main basic fabrics to each other, and vent holes are defined in the side basic fabric corresponding to a front surface of the deployed air bag. By the fact that the vent holes are defined in the front surface of the air bag in the above described manner, the vent holes can be prevented from being occluded by a door and/or an occupant upon deployment of the air bag.
However, if the air bag is formed by sewing the three basic fabrics together as in the above-described known occupant protecting device of JP ""054, the number of parts and the number of manufacturing steps are increased. Therefore, it is conceived that an air bag is formed from a single basic fabric. More specifically, an air bag 03 shown in FIG. 15B can be formed by double-folding a single basic fabric 01. cut into a substantially band-like shape at a central folding line 02, as shown in FIG. 15A, and sewing outer peripheral portions of the folded basic fabric 01 excluding the folding line 02 together. In this case, there is a problem that it is impossible to define vent holes 04, so that the vent holes 04 lie on a sewing portion 05. Therefore, the positions of the vent holes are deviated laterally from a front surface of the air bag 03 and as a result, when the air bag 03 has been expanded, the vent holes 04 are occluded by a door and/or an occupant.
Accordingly, it is a first object of the present invention to ensure that an air bag provided within a seat back is deployed obliquely forwardly, so that the air bag is permitted to reliably penetrate into a space between an occupant and an inner surface of a side of a vehicle body.
It is a second object of the present invention to provide an occupant protecting device designed so that an air bag accommodated within a seat back is deployed between an occupant and an inner surface of a side of a vehicle body upon collision of a vehicle, wherein the vertical deployment of the air bag is carried out promptly.
It is a third object of the present invention to ensure that an air bag functioning upon a side collision and including vent holes in its front surface is formed with a smaller number of parts.
To achieve the first object, according to a first aspect. and feature of the present invention, an occupant protecting device is provided which comprises: an air bag accommodated in a folded-up state within a seat back of a seat on which an occupant sits down, wherein when the air bag is expanded by a gas generated by an inflater, the air bag is deployed between the occupant and an inner surface of a side of a vehicle body, the air bag having a rear-side base portion fixed to a fixing member, and a front-side foldable portion folded up in a longitudinal direction, and the base portion having a surplus section provided thereon at a location remote from the inner surface of the side of the vehicle body for permitting the movement of the foldable portion toward the inner surface of the side of the vehicle body.
With the above-described arrangement, when the foldable portion of the air bag is expanded by the gas generated by the inflater, the foldable portion can be moved toward the inner surface of the side of the vehicle body by the surplus section provided on the base portion of the air bag at the location remote from the inner surface of the side of the vehicle body. Therefore, the air bag can be deployed obliquely forwardly to reliably penetrate into a space between the occupant and the inner surface of the side of the vehicle body.
In addition, to achieve the above-described first object, according to a second aspect and feature of the present invention, an occupant protecting device is provided which comprises: an air bag is accommodated in a folded-up state within a seat back of a seat on which an occupant sits down, wherein when the air bag is expanded by a gas generated by an inflater, the air bag is deployed into a space between the occupant and an inner surface of a side of a vehicle body, inner and outer (as viewed from inside of the vehicle body) portions of the air bag being folded up to form pleats, the number of the pleats on the inner portion being set smaller than the number of the pleats on the outer portion.
With the above-described arrangement, when the foldable portion of the air bag is expanded by the gas generated by the inflater, the inner portion (as viewed from inside of the vehicle body) of the air bag, having the smaller number of the pleats, is expanded earlier than the outer portion, having the larger number of the pleats. Hence, the inner portion (as viewed from inside of the vehicle body), which is expanded earlier, urges the outer portion in an outward direction of the vehicle body. As a result, the air bag can be deployed obliquely forwardly to reliably penetrate into the space between the occupant and the inner surface of the side of the vehicle body.
To achieve the second object of the present invention, according to a third aspect and feature of the, present invention, a process for folding up an air bag in an occupant protecting device which is designed so that the air bag, accommodated in a folded-up state within a seat back of a seat on which an occupant sits down, is expanded by a gas generated by an inflater, whereby the air bag is deployed between the occupant and an inner surface of a side of a vehicle body, the process comprising: a first step of folding the air bag into a bellows-like shape in a longitudinal direction of a vehicle body; and a second step of vertically folding at least one of upper and lower portions of the air bag folded in the bellows-like shape.
With the above-described feature, when the air bag is deployed by the gas generated by the inflater upon collision of a vehicle, at least one of the upper and lower portions of the air bag folded vertically at the second step is first deployed vertically, and then, the air bag folded in the longitudinal direction at the first step is deployed longitudinally. By deploying the air bag vertically and then longitudinally in the above manner, a side of an occupant can be held back at an initial stage of the deployment over a vertical wide range.
In addition to the third feature, if the vertical dimension of the inflater and the vertical dimension of the air bag folded at the second step are substantially equal to each other, the dimensions of the air bag in the folded-up state can be reduced to provide a compactness of an air bag module, while increasing the vertical dimension of the air bag to enable the side of the occupant to be held back over the wide range.
To achieve the third object, according to a fourth aspect and feature of the present invention, an occupant protecting device comprises: an air bag which is adapted to be expanded by a gas generated by an inflater upon side-collision of a vehicle, whereby the air bag is deployed from the inside of a seat back along an inner surface of a door in a forward direction of a vehicle body, the air bag having vent holes in its front surface, and the air bag being formed by sewing a single basic fabric at a location of the front surface of the air bag.
With the above-described arrangement, the air bag is formed by sewing the single basic fabric and therefore, the number of parts and the number of manufacturing steps can be suppressed to the minimum. In addition, the sewing portion lies at the location of the front surface of the air bag. Therefore, the vent holes can be provided in the front surface of the air bag without interference with the sewing portion, whereby the vent holes can be prevented from being occluded by a door and/or an occupant, when the air bag is deployed.
In addition to the fourth feature, if the air bag is formed by folding a band-like basic fabric in half at a folding line, and sewing outer peripheries of the folded fabric portions excluding the folding line, and the vent holes are defined to lie on the folding line, the shape of the basic fabric can be simplified, and the amount of the sewing operation can be suppressed to the minimum.